util/oslib: Have qemu_prealloc_mem() handler return a boolean

Following the example documented since commit e3fe3988d7 ("error:
Document Error API usage rules"), have qemu_prealloc_mem()
return a boolean indicating whether an error is set or not.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-Id: <20231120213301.24349-19-philmd@linaro.org>

include/qemu/osdep.h

@@ -678,8 +678,10 @@ typedef struct ThreadContext ThreadContext;
  * memory area starting at @area with the size of @sz. After a successful call,
  * each page in the area was faulted in writable at least once, for example,
  * after allocating file blocks for mapped files.
+ *
+ * Return: true on success, else false setting @errp with error.
  */
-void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+bool qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
                        ThreadContext *tc, Error **errp);
 
 /**

util/oslib-posix.c

@@ -497,7 +497,7 @@ static bool madv_populate_write_possible(char *area, size_t pagesize)
            errno != EINVAL;
 }
 
-void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+bool qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
                        ThreadContext *tc, Error **errp)
 {
     static gsize initialized;
@@ -506,6 +506,7 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
     size_t numpages = DIV_ROUND_UP(sz, hpagesize);
     bool use_madv_populate_write;
     struct sigaction act;
+    bool rv = true;
 
     /*
      * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
@@ -534,7 +535,7 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
             qemu_mutex_unlock(&sigbus_mutex);
             error_setg_errno(errp, errno,
                 "qemu_prealloc_mem: failed to install signal handler");
-            return;
+            return false;
         }
     }
 
@@ -544,6 +545,7 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
     if (ret) {
         error_setg_errno(errp, -ret,
                          "qemu_prealloc_mem: preallocating memory failed");
+        rv = false;
     }
 
     if (!use_madv_populate_write) {
@@ -555,6 +557,7 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
         }
         qemu_mutex_unlock(&sigbus_mutex);
     }
+    return rv;
 }
 
 char *qemu_get_pid_name(pid_t pid)

util/oslib-win32.c

@@ -264,7 +264,7 @@ int getpagesize(void)
     return system_info.dwPageSize;
 }
 
-void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+bool qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
                        ThreadContext *tc, Error **errp)
 {
     int i;
@@ -274,6 +274,8 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
     for (i = 0; i < sz / pagesize; i++) {
         memset(area + pagesize * i, 0, 1);
     }
+
+    return true;
 }
 
 char *qemu_get_pid_name(pid_t pid)